You aren't going to find one "perfect" sign for "trick or treat."
TRICK-or-TREAT
Here is a version that uses a combination of the signs "DECEIVE" and
"CANDY"




TRICK-or-TREAT
Here is a version of "trick or treat" that I figure started out as a
combination of "TEASE" or "GIVE-to-me."
A friend of mine said he saw this being done by young students at
"Fremont." (California School for the Deaf "CSD" in Fremont,
California.) That was around 2007. It will be
interesting to see if this version sticks around or spreads:





